async function processWrite()

in firestore-send-email/functions/src/index.ts [294:343]
42 lines of code
11 McCabe index (conditional complexity)

async function processWrite(change) {
  if (!change.after.exists) {
    return null;
  }

  if (!change.before.exists && change.after.exists) {
    return processCreate(change.after);
  }

  const payload = change.after.data() as QueuePayload;

  if (!payload.delivery) {
    logs.missingDeliveryField(change.after.ref);
    return null;
  }

  switch (payload.delivery.state) {
    case "SUCCESS":
    case "ERROR":
      return null;
    case "PROCESSING":
      if (payload.delivery.leaseExpireTime.toMillis() < Date.now()) {
        // Wrapping in transaction to allow for automatic retries (#48)
        return admin.firestore().runTransaction((transaction) => {
          transaction.update(change.after.ref, {
            "delivery.state": "ERROR",
            // Keeping error to avoid any breaking changes in the next minor update.
            // Error to be removed for the next major release.
            error: "Message processing lease expired.",
            "delivery.error": "Message processing lease expired.",
          });
          return Promise.resolve();
        });
      }
      return null;
    case "PENDING":
    case "RETRY":
      // Wrapping in transaction to allow for automatic retries (#48)
      await admin.firestore().runTransaction((transaction) => {
        transaction.update(change.after.ref, {
          "delivery.state": "PROCESSING",
          "delivery.leaseExpireTime": admin.firestore.Timestamp.fromMillis(
            Date.now() + 60000
          ),
        });
        return Promise.resolve();
      });
      return deliver(payload, change.after.ref);
  }
}